AGa₃F₆(SeO₃)₂ (A = Rb, Cs): A New Type of Phase-Matchable Hexagonal Tungsten Oxide Material with Strong Second-Harmonic Generation Responses

Abstract

Combining a wide band gap, strong secondharmonic generation (SHG), and good phase matchability into a single structure is an ongoing challenge in the design of nonlinear optical (NLO) materials. Herein, we report the first examples of fluorinated gallium selenites AGa 3 F 6 (SeO 3 ) 2 [A = Rb (RGFS), Cs (CGFS)] by introducing fluorinated main-group metal octahedra [GaO 2 F 4 ] into the metal selenite system. The two new compounds are isostructural (noncentrosymmetric space group P6 3 mc) and feature interesting hexagonal tungsten oxide (HTO)-type [Ga 3 F 6 (SeO 3 ) 2 ] ∞ layers, with alkali metal cations acting as linkers between these layers while also maintaining charge balance. Photophysical studies demonstrate that RGFS and CGFS exhibit strong phase-matchable SHG responses [5.6 × KH 2 PO 4 (RGFS) and 5.4 × KH 2 PO 4 (CGFS) at 1064 nm], high laser damage thresholds [39.37 MW/cm 2 (RGFS), 41.59 MW/cm 2 (CGFS) at 1064 nm, 10 ns pulses, 1 Hz repetition rate], wide band gaps [3.57 eV (RGFS), 3.65 eV (CGFS), the latter the highest value among polar HTO-type selenites or tellurites], and large birefringences (0.097 and 0.092 at 546 nm for RGFS and CGFS, respectively); the two compounds simultaneously exhibit multiple key NLO parameters for practical applications in the near-ultraviolet and mid-infrared region. The critical role of the [GaO 2 F 4 ] 5− groups in the linear and NLO responses in the two materials has been elucidated by first-principles studies. Our report demonstrates that introducing fluorinated main-group metal octahedra into metal selenite systems can lead to promising multicomponent selenite NLO materials.

The Combination of Structure Prediction and Experiment for the Exploration of Alkali‐Earth Metal‐Contained Chalcopyrite‐Like IR Nonlinear Optical Material

“…[ 15,28,33,39 ] What's more, the refractive index difference (RID) of DCL‐MgGa 2 Se 4 was investigated by the polarizing microscope method. [ 4d,10,11,40 ] The optical path differences of the DCL‐MgGa 2 Se 4 crystal at 546 nm were 1.48 µm, and the thickness of the crystal was measured to be 31 µm (Figure S8, Supporting Information). According to the Equation () in the Experimental Section, the RID was calculated to be ≈0.048 at 546 nm, which is consistent with the PM behavior.…”

“…5 pol) with Berek compensator. [ 4d,10,11,40 ] The wavelength of the light source was 546 nm. The RID value is calculated by the following formula: $$\begin{equation} R=\left|{N}_{g}-{N}_{p}\right|\ensuremath{\times{}}T= \Delta n\ensuremath{\times{}}T \end{equation}$$in which R represents the optical path difference; N g , N p , and Δ n means the refractive index of fast light and slow light, the RID, respectively, and T denotes the thickness of the crystal.…”

CsZrF4(IO3): The First Polar Zirconium Iodate with cis-[ZrO2F6] Polyhedra Inducing Optimized Balance of Large Band Gap and Second Harmonic Generation

“…Second-order nonlinear optical (NLO) materials are of great commercial and academic significance owing to their applications as optical frequency multipliers, optical parametric amplifiers, electro-optic rectifiers, etc. − For a practical NLO crystalline material, it is necessary to simultaneously satisfy several capability requirements, including strong second-harmonic generation (SHG; >3 × KH 2 PO 4 (KDP)), large optical band gap (>3.0 eV), high laser damage threshold (LDT), wide transparency window for broad-spectrum adaptability, moderate birefringence for phase-matching (PM) behavior, and good chemical and physical stability. − However, there are intricate relations between these key functions: SHG performance and optical band gap are mutually conflicting , and a wide band gap usually corresponds to a high LDT but small birefringence . As a result, it is highly challenging to optimize these diverse properties in one material.…”

A2MoO2F3(IO2F2) (A = Rb, Cs): Strong Nonlinear Optical Responses and Enlarged Band Gaps through Fluorine Incorporation

“…To date, borate and phosphate NLO crystals have been applied practically from DUV to visible (Vis) regions, − yet the applications of IR NLO crystals, such as AgGaX 2 ( X = S or Se), ZnGeP 2 , SnI 4 ·(S 8 ) 2 , and Ga 2 Se 3 , were impeded by the drawbacks of comparatively small laser damage thresholds (LDTs). It is therefore emergent to synthesize new IR NLO crystals that can combine a strong second-harmonic generation (SHG) response and a high LDT together. , …”